A newly identified disease is moving rapidly through livestock in Europe and has authorities both worried and puzzled. The disease, dubbed Schmallenberg virus for a town in west-central Germany where one of the first outbreaks occurred, makes adult animals only mildly ill, but causes lambs, kids and calves to be born dead or deformed.

The United Kingdom’s Animal Health and Veterinary Laboratories Agency (AVHLA) said today that the virus has been found on 29 farms in England; in the past few weeks they found it in sheep, but today announced that they have identified it in cattle as well. In mainland Europe, it has been identified on several hundred farms in the Netherlands, Germany and Belgium, and most recently in France. The European Center for Disease Prevention and Control has said that the new virus’s closest relatives do not cause disease in humans — but that other more distantly related viruses do:

The new virus belongs to the Bunyaviridae family, genus Orthobunyavirus, Simbu serogroup (preliminary information, based solely on genetic information)… Genetic characterisation has shown that the new virus is closest to the following Simbu serogroup viruses: Shamonda-, Aino- and Akabane-viruses, which do not cause disease in humans. However, at least 30 orthobunyaviruses are zoonotic and may cause disease in humans, with symptoms ranging from mild to severe — e.g. La Crosse encephalitis virus, California Encephalitis virus, Cache Valley virus, Batai virus, Tahyna virus, Inkoo virus, Snowshoe Hare virus, Iquitos virus and Oropouche virus.

The past few days have seen the simultaneous publication of the first vetted medical-journal pieces on the vast European outbreak of E. coli O104. They’re fascinating for what they report that is new about this perplexing epidemic — now up to 3,802 cases including 43 deaths, according to the World Health Organization — and also for the further questions they raise.

Possibly most headline-worthy: Two reports in Eurosurveillance, Europe’s peer-reviewed open-access epidemiology journal, that suggest this strain is communicable from person to person and also produces unusual and troubling symptoms.

The stream of news from the E. coli O104:H4 outbreak in Germany has been so steady that it’s been hard to catch my breath long enough to post on it. The Robert Koch Institute in Germany said today that they think the epidemic curve is cresting, which makes me unusually late to the party. Nevertheless, since there are likely to be more cases and more deaths — and a long struggle still to understand what happened — I thought it would be useful to count up the things that we can say for sure, and those that remain puzzlingly open questions.

First: Is this the largest E. coli outbreak ever? According to food-safety uber-attorney Bill Marler, this outbreak — more than 2,600 victims, 13 countries, 26 deaths (Nature News has a great graphic of cases by country) — is dwarfed only by a 1996 epidemic in Japan. (Here’s Marler’s list). If it’s not the largest, it is likely to have produced the largest percentage of serious illness: As of today, there are 725 cases of hemolytic uremic syndrome (689 in Germany, 33 in the rest of Europe, three in the United States), according to WHO-Europe.